The present invention relates to a spotlight projector for overhead travelling cranes which employs a very high pressure mercury lamp as its light source and is mounted on an overhead travelling crane to spotlight a lifting device.
Generally, when an overhead travelling crane is operated, it is an essential operating requirement for the operator of the overhead travelling crane to ascertain an object to be lifted or the engagement of the object with the lifting device by viewing or visual observation. Particularly, in the case of large cranes, the importance of this problem is further increased by the special uses of these cranes. For instance, in the case of a so-called ladle crane having a large capacity as compared with those of other cranes used in an iron works, the crane is used to carry the molten iron to and away from the mixer, or carry the molten iron to the open-hearth furnace and carry away the molten steel from the open-hearth furnace and its capacity in terms of the total weight, i.e., the sum of the weight of the ladle and the weight of its content is far in excess of 200 tons. Moreover, there are many cases where the overhead travelling crane is used continuously day and night and thus there are instances where satisfactory accomplishment of the previously mentioned essential operating requirement is made extremely difficult depending on the type of objects to be lifted, the conditions of the working environment, etc.
For instance, when a molten iron charging ladle is to be lifted in an iron works or the like where the crane is continuously operated day and night as mentioned previously, the operator of the crane frequently experiences that the operator is blinded by the radiant light rays of a high relative brightness emitted from the surface of the molten iron in the molten iron ladle and the operator finds it extremely difficult to ascertain by visual observation the lifting device as well as the surrounding objects other than the molten iron ladle itself. Particularly, during the crane operation for bringing the hoisting hooks from the traversing car near the trunnions on the molten iron ladle or the operation of engaging the hooks with the trunnions, it is extremely difficult for the operator to check up the hooks and the trunnions through visual observation and this presents an operating difficulty. In particular, during the night operation, the operating difficulties due to such causes tend to become increasingly serious considerably with the result that not only these problems involve the possibility of causing serious error or accidents but also they must be studied from the standpoint of safety supervision.
Although an attempt has been made to overcome the foregoing difficulties by providing large projectors in the work site to illuminate the important places, the foregoing operating difficulties have not be overcome completely.